I am stuck in this problem. Please help!

- In preparation of a dinner party Mary takes a large slab of salmon out of her freezer(kept at 28° F) and place in her 43°F refrigurator . Six hours later the temperature of the salmon is31°.

(a) Find the temperature of the salmon > hours after it is placed into the refrigerator.

(b) How long will it take for the salmon is 40°F